[codex] Add AST analysis and agent navigation maps

[itsflaid]

Summary

• add a normalized analyzer registry with ts-morph for JavaScript and TypeScript plus heuristic and fallback analyzers
• generate a compact .devmap/index.json and focused .devmap/features/*.json maps
• switch generated agent guidance to index-first navigation with explicit sourcePriority ordering
• classify documentation, landing UI, CLI, analysis, snapshot, and AI roles before technical feature attribution
• replace file-list flows with behavioral structural flows and improve agent-oriented critical-file selection

Why

The previous snapshot was useful as a full archive, but too large as an agent entry point. Feature attribution could also treat prompt examples, documentation, or landing copy as runtime capabilities such as Authentication.

Impact

Agents can start from a roughly 4.5 KB index, open one relevant feature map, and inspect a small prioritized source set. The full snapshot remains backward compatible.

Verification

• pnpm test:cli (96/96)
• pnpm --filter devmap build
• pnpm test:package-e2e
• manual source-mode analyze on DevMap
• git diff --check